College level biochem question on Krebs cycleno idea where t

College level biochem question on Kreb\'s cycle--no idea where to start/

In the presence of saturating amounts of oxaloacetate, the activity of citrate synthase from pig heart tissue shows a sigmoid dependence on the concentration of acetyl-CoA, as shown in the graph below. When succinyl-CoA is added, the curve shifts to the right and the sigmoid dependence is more pronounced. On the basis of these observations, suggest how succinyl-CoA regulates the activity of citrate synthase. Why is succinyl-CoA an appropriate signal for regulation of the citric acid cycle? How does the regulation of citrate synthase control the rate of cellular respiration in pig heart tissue?

Solution

Succinyl CoA acts as an inhibitor of citrate synthase by competing for the active site.

Succinyl CoA regulates the citric acid cycle by inhibiting the enzyme citrate synthase that converts oxolacaetate and acetyl CoA to form citrate thus stoping it from entering citric acid cycle when the energy supply is already high.

Regulation of citrate synthase reduces the respiration rate in pig heart tissue by inhibiting the citric acid cycle as the energy supply is already high.